Looking for a HTML range field in Drupal 8 core I did not found one. First I tried to alter Number Widget but that was wrong. Just extend a suitable widget. The code is very short. But the display is not as good as one needs. Where is the min and max value? And the current value? The specs @ w3c html5 forms input range has some user agent rendering which does not give min, max or current value hints.

number field.